Double world champion Max Verstappen clocked the fastest time in the third and final practice on Saturday for the Australian Grand Prix, but his Red Bull teammate Sergo Perez had a horror session to finish sixth.
The early championship leader posted a blistering best lap of one minute 17.565 seconds around Melbourne's Albert Park, 0.162secs ahead of Aston Martin's Fernando Alonso, who again confirmed his pace and potential.
But Perez, who took pole at the last grand prix in Saudi Arabia and translated it to victory, battled persistent problems.
He was still in garage as mechanics worked on his car 20 minutes into the hour-long session.
When he finally emerged -- the last driver out -- he was caught in traffic, then ran onto the gravel, skidded as he tried to put a fast lap together, then hit the gravel again late on.
Alpine's Esteban Ocon was a surprise third, ahead of Mercedes' George Russell and Pierre Gasly in the other Alpine.
Ferrari's Carlos Sainz was seventh, but his teammate Leclerc, last year's Australian winner, ended a disappointing 13th.
Seven-time world champion Lewis Hamilton, a two-time Melbourne winner and eight-time Australian pole-sitter, was eighth.
Lance Stroll in an Aston Martin took ninth with China's Zhou Guanyu, who spun his Alfa Romeo and clipped the barriers, rounding out the top 10.
On a cool and overcast day, Sainz, on soft tyres, set the early pace but was quickly toppled by the flying Verstappen with drivers keen to get in fast early laps ahead of forecast rain, which didn't materialise.
Sainz again took over, ahead of Alonso, and it stayed that way till a red flag came out with 26 minutes left for debris on the track, seemingly from Nick de Vries' AlphaTauri.
When the cars returned, Verstappen, on softs, showed who was boss to post a new fastest lap, with Alonso his nearest challenger.